Okay, so. Where is your:
1. Example of work(s)? (maps, sprites, sounds, musics, etc.)
And hope you don't mind me being blunt, but:
1. No one cares what a region based of. You can based it on poop, on candy, on lollipop, on real continent or island. What important is, you got a map for your pokes. Of course you are free to describe from what you based them from.
2. A story may or may not need an antagonist team. Or heck, it doesn't need to be a team. You could make it so the player needs to fight last boss on first encounter. Satan, for example. Or maybe all of the encounters are mid boss level. What important is, you got a plot, and that's what your story for. And to repeat, no one cares what they are based of. And to repeat again, Of course you are free to describe from what you based them from.
3. Gym leaders are part of the story. Your story could use them, or exclude them entirely. And to repeat again, no one cares what they are based of, or even their gender. You are free to describe from what you are based of and their gender. You could station an AI, a tree, a gender confused person, a round smooth rock, to be a gym leader. Heck, they are all tiles, I bet you could station a simple dirt road as a gym leader.
4. A region may or may not have legendary pokes. And to repeat again, no one cares if they fit or not in the story. You could make them fit, or you could not. You could say, you have a legendary pure rock type pokemon, in underwater region. Hell, that doesn't sound fit at all? Oh, but it is. How do you think a rock type pokemon able to survive in underwater? Well, it's a legendary.
All the rules you proposed are simply elements that make your story interesting
, not something you MUST
TL;DR; Cook up something exciting and interesting so the OP(original poster, if you don't get that) is interested in your application. And then we can have additional region to play at. Because, who doesn't like moar regions? Especially if they are interesting to explore.Edited 2 weeks ago by Arthzalcotl.